Manufacturers of internal combustion engines, particularly diesel engines, are presented with the challenging task of complying with current and future emission standards for the release of nitrogen oxides, particularly nitrogen monoxide, as well as unburned and partially oxidized hydrocarbons, carbon monoxide, particulate matter, and other particulates. In order to reduce the emissions of internal combustion engines, an exhaust gas treatment system is used to convert certain, or all of these exhaust constituents into non-regulated exhaust gas components and reduce particulates from the exhaust gas flowing from the engine.
An exhaust gas treatment system typically includes one or more treatment devices, such as oxidation catalyst (OC) devices, selective catalyst reduction devices, particulate filters, mixing elements and urea/fuel injectors. Some emission standards mandate that these components of an exhaust gas treatment system have separate diagnoses, specifically a separate diagnosis for an OC device. Therefore, a diagnostic scheme for diagnosing an OC device is desirable.